1. Field of the Invention
This invention relates to power tool handles and, more particularly, to a handle for manually using a power bit and having a quick release chuck for securing the power bit to the handle.
2. Description of the Prior Art
The term "power bit" refers to elements typically used for driving fastener devices, such as screws, nuts, and bolts. The most commonly used power bits generally have a hexagonally configured shank and a groove extending about the shank with a flat portion disposed at the bottom of the groove between two radiused portions. Such power bits have been used since at least 1930, adn their use has increased substantially in recent years. The American National Standards Institute has a specification for such tools known as ANSI B107.4-1973. The standard refers to driving and spindle ends for power bits for portable hand, air, and electric tools.
The power bits are typically used with electric and air driven tools, but the use of manual hand tools with such power bits is virtually nil, even though the use of power bits with hand-held power tools goes back in time more than fifty years, and during that long time period the number of tools or tool bits accumulated in the field is enormous. In the known prior art dealing with power tool holding devices for power bits, there are primarily two types of chucks used. One type is a quick release type having apparatus similar to that in U.S. Pat. No. 4,184,692, which patent will be discussed below.
The similar, but not shown, quick release chuck utilizes a ball retained in a groove in the shank of the power bit. The ball is trapped between a spring biased movable sleeve and the bottom surface of the tool groove. In this configuration, the ball is free to move in and out radially with respect to the longitudinally axis of the tool because of necessary manufacturing tolerances and clearances. It is additionally free to move in the axial direction by virtue of a flat on the bottom of the groove as specified in the aforementioned ANSI standard. The ball is accordingly loose and free to move both axially and radially. Positive holding of the tool against an extraction force is not accomplished until sufficient axial movement of the tool has taken place to wedge the ball between the back radius of the tool groove and the surface of the sleeve bore. On a one-fourth inch hexagonal power bit this can exceed one-tenth inch. This distance has been confirmed by measurement on currently manufactured quick release chucks of this type. This looseness is objectionable on a hand tool.
The second type of holder is a non-quick release type. U.S. Pat. No. 3,726,533 discloses one such chuck. A pin is trapped in the groove in the power bit shank to provide a frictional force on the bit. In the alternative, a ball may be loaded by an annular split spring or by a coil spring to press against the bottom of the groove in the power bit shank. The force against the pin or ball acts only radially inwardly against the bit, and thus also allows longitudinal movement of the bit in the chuck. As the pin or ball contacts the radius of the tool groove, normal forces develop on the radius which tend to hold the tool against further longitudinal or axial movement. For spring biased balls, when the radial component on the ball exceeds the spring force, the tool bit will break loose.
It will be noted that a spring force high enough to dampen the longitudinal movement of the bit will also require very high axial extraction forces to remove a power bit and to insert another bit. Usually another tool, such as pliers or even a vise, may be required for such removal and insertion, unless the spring force can be reduced for the insertion and removal steps.
Examples of quick release chucks similar in principal to the quick release chuck discussed above, with reference to U.S. Pat. No. 4,184,692, are U.S. Pat. Nos. 1,602,708 and 2,618,940. The feature common to these patents is a detenting ball which is entrapped between a sleeve and a recess. However, the ball is loose and is without constant bias.
The '692 and '708 patents utilize a plurality of balls detenting into dimples in a cylindrical tool shank. The dimples and trapped ball provide resistance to both rotational and lateral movement of the tool relative to the spindle of the chuck, but only after tolerance and clearance spacing is taken up. The '940 patent likewise utilizes a plurality of balls trapped by a sleeve in a groove. A spline is utilized for rotational locking.
The following are examples of quick change chucks which utilize frictional forces alone on the surface of a tool shank. These are characterized by a ball or by a plurality of balls biased by a camming surface on a spring actuated sleeve against a non-detented surface on the tool or part to be held. The resulting force is a purely normal force, acting entirely in a radial direction, with no component in the axial direction. This creates a purely frictional force on the tool or part to be held. Obviously, this is a non-positive holding force which will release when the pull out force exceeds the essentially constant frictional force. U.S. Pat. Nos. 945,603, 3,521,895 and 3,762,732 are examples of these characteristics.
U.S. Pat. Nos. 3,893,677 and 4,395,051 are examples of quick change tool holders for power driven spindles which utilize a plurality of balls biased against tool holder surfaces which are configured such that under a pull out force, the normal force on the tool holder has a component in the axial direction. The tangential and normal forces between the tool holder and the sleeve combine to create a wedging or locking action.
U.S. Pat. No. 4,202,557 utilizes a spring bias a sleeve. The sleeve applies pressure against a wedge or drive member to hold a tool in place.
It will be noted that most of the above-discussed patents refer to large power tool chucks, as opposed to hand tool holders or chucks. Moreover, in most cases, movement of the tools in longitudinal or axial directions is not a problem. However, in hand tool usage, axial movement is very much of a problem, and is accordingly very undesirable.
Some of the prior art patents disclose, in non-tool or non-hand tool environments, wedging lock systems in which no axial movement takes place. However, none of those type locking systems is directly applicable or adaptable to hand tools.
The apparatus of the present invention is designed for hand tool usage. Axial movement does not occur.
The apparatus of the present invention uses a combination of normal and tangential forces to hold a power bit tool in place within a chuck of a handle for a hand tool. The normal and tangential forces, as applied by the apparatus of the present invention, securely lock the tool bit in place to a handle without allowing longitudinally or axial movement of the bit.